I don't know enough here to say anything definitively, but I think knowing there's a conflict is half the battle. UTC timestamps are great but clocks have to be

I don't know enough here to say anything definitively, but I think knowing there's a conflict is half the battle. UTC timestamps are great but clocks have to be perfectly in sync which is unlikely even w/ NTP. And as you mentioned doesn't withstand users changing their system time. Sometimes bubbling conflict resolution up to the user is a good idea. It's preferable to data loss.